I don't know... Glassdoor's system seems to work pretty well for collecting this kind of data. Sure the number of reported salaries is maybe too small to say anything specific about individual companies, but in aggregate places like Glassdoor and LinkedIn could probably tell us with high certainty what the distribution looks like.
In a world where (A) compensation is typically mostly in the form of liquid equity grants and (B) compensation amounts change rapidly year-on-year, Glassdoor's system vastly understates compensation in the field.
